Page 316 - Design for Six Sigma a Roadmap for Product Development

286 Chapter Nine

Besides the main basic function, there are other useful functions as
well; we can call them secondary useful functions. There are several
kinds of secondary useful functions:
1. Secondary basic functions. These are not main basic function, but
customers definitely need them. For example, “providing a comfort-
able riding environment” is a “must have” for automobiles.
2. Nonbasic but beneficial functions. These functions provide cus-
tomers with esteem value, comfort, and so on. For example, the
paint finish in automobiles provides both basic and nonbasic func-
tions; it protects the automobile from corrosion and rust, and cre-
ates a “sleek look” for the car.

Besides secondary useful functions, there are two other types of functions:
1. Supporting function. This function supports the main basic func-
tion or other useful function. It results from the specific design
approach to achieve the main basic function or other useful func-
tions. As the design approach to achieve the main basic function
and other useful functions are changed, supporting functions may
also change. There are at least two kinds of supporting functions:
assisting functions and correcting functions.
■ Assisting functions. These functions assist other useful func-
tions. For example, the engine suspension system provides the
function of “locking the position of the engine in the automobile”
to enable the engine to remain securely in place on the car while
providing power.
■ Correcting functions. These functions correct the negative effects
of another useful function. For example, the main basic function of
the water pump in the automobile internal-combustion engine is to
“circulate water in the engine system in order to cool the engine off ”;
it is a correcting function for the automobile engine. The main basic
function of the engine is to provide power for the automobile, but the
internal-combustion engine also creates negative effects, such as
heat. A water pump’s function is to correct this negative effect. If we
change the design and use electricity as the power source of the
automobile, the function of a water pump will no longer be needed.

2. Harmful function. This is an unwanted, negative function caused
by the method used to achieve useful functions. For example, an
internal-combustion engine not only provides power but also gener-
ates noise, heat, and pollution, and these are harmful functions.

In summary, the main basic function and secondary useful functions
provide benefits for the customer. Supporting functions are useful,